V8 Supercars are set for one of the most closely contested series in years after successful testing on the new-look cars for the 2013 championship, says chairman Mark Skaife.

The vehicle bodies and aerodynamic kits of the four manufacturers to line up on the grid have been approved for competition in the expanded championship which sees Nissan and Mercedes join regulars Holden and Ford.

The cars were approved following six days of intensive testing and evaluation to determine the bodywork and aerodynamic specification of each vehicle.

All four models now have the closest aerodynamic parity of any makes in the history of the sport and are within half a per cent of each other in terms of relative aerodynamic efficiency, the sport's governing body said.

And the public will see them for the first time at the compulsory pre-season V8 Supercar test day at Sydney Motorsport Park on February 16 ahead of the series opener two weeks later in Adelaide.

"Fans will see the most hotly contested championship in years based on the results of these tests," former champion driver Skaife said.

"It was the most technically demanding project we have ever undertaken, especially when you consider the different body shapes and design characteristics of each of the cars."

All four of the vehicle bodies and aero kits are within 2kg of overall downforce and 2kg of drag of each other.

"To have all of the 2013 vehicles within two kilograms, which is 0.56 per cent of total downforce is a remarkable achievement," Skaife said.

"The results of these tests will facilitate the most fair and equitable competition we have ever seen."

V8 Supercars CEO David Malone said the completion of aerodynamic testing was a step towards a milestone season for the sport.

"This is the culmination of five years of hard work, intensive planning and preparation to have these new cars on the grid as the sport enters the new era," Malone said.